A query
about what a virgin forest is made me wonder about people's knowledge
of common environmental terms. To effectively discuss any subject, one
needs a clear understanding of the terms and expressions that help define
the topic. What follows is a short environmental lexicon of some terms
I have been asked to define.

Virgin forest.
Some of today's younger generation seem to be unclear on the meaning,
possibly because we have so few virgin forests left. The original meaning
is simple, from the word meaning "chaste," representing a forest
that has never been timbered and in which the dominant, old-growth tree
species have reached their maximum ages. By the beginning of this century,
the United States had lost more than 99 percent of the virgin forests
that had been on the continent at the time of European settlement.

Vast areas
of longleaf or loblolly pine stands, cypress-gum swamps, redwood and Douglas
fir or oak-hickory forests once covered the land. Only remnants remain
of most. A forest once cut will not reach old-growth, virgin forest status
during our lifetimes. However, some forests that were timbered almost
a century or more ago, such as the Okefenokee Swamp, are beginning to
be impressive again. Where they exist, these formerly sullied but now
reborn forests deserve our appreciation. Let's not let them lose their
reputations again.

Deforestation.
An appropriate term to follow virgin forest, "deforestation"
means to remove the trees (or forests). To many environmentalists, deforestation
is equated with tree removal by logging companies. But deforestation can
be a consequence of building highways, shopping malls, and apartment complexes
or of converting land to agricultural use. In fact, these activities might
be called "permanent deforestation." At least a forestry operation
replants new trees to replace those it removes.

Greenhouse effect. A greenhouse operates on a simple principle: Light
passes through a clear ceiling and the warmth created is trapped within,
heating up the insides of the structure. Scientists concerned about global
warming view earth as operating like a greenhouse. Some models predict
that continual production of the high levels of CO2 resulting from an
industrial world will create a blanket around the earth that allows light
in but impedes heat from escaping to outer space. If global warming raises
temperatures several degrees, some scientists predict that that changes
in the earth's climates could have severe impacts on agriculture and on
everyday living.

The dilemma
about the greenhouse effect and global warming is that while an increase
in CO2 has been detected, it has been difficult to demonstrate that it
is linked to appreciable changes in atmospheric temperatures on a worldwide
basis. Some scientists remain skeptical about whether the issue is one
to worry about; others stake their reputations on their belief that it
is a problem and that people are the cause.

Genetic engineering.
Since the 1980s, studies in genetics have overwhelmed the field of biology.
We know more than ever about chromosomes and the genes they carry, and
we know about DNA and other materials inside genes. Geneticists are now
able to substitute one gene for another in an organism, actually rebuilding
the genetic structure that directs an organism's development, behavior,
and physiology. Genetic engineering promises great advancements for controlling
certain environmental processes.

In agriculture,
enormous strides have been made toward producing pest-resistant crops,
genetically modifying the pests themselves, or producing more effective
predators on the pests. Will all be well in the field of crop production
with genetic engineers at work? Could be, but we must proceed with caution,
remembering that engineers handling other aspects of the environment have
done much good but have also caused a few environmental train wrecks.

Environmentalism.
Environmentalism is sometimes viewed as an emotional response that is
based on insufficient scientific guidance. Yet people opposed to environmentalism
can also respond emotionally, with equally insufficient levels of scientific
knowledge. Effective environmental awareness is based on a foundation
of findings by ecologists who, like other scientists, must be objective.
Results of ecological studies can help scientists and laypeople make informed
choices about our environment. Which brings us full circle, for to understand
the findings, we have to understand the terms used to describe them.